CB9

• Seismic surveys in the North Sea have reduced the numbers of microscopic animals that sandeels feed on
• Distribution of organisms


  Where they are found in an ecosystem
• Factors affecting distribution of organisms


  • Physical and chemical factors, such as temperature, rainfall and substances in the soil
• Abiotic factors


  Non-living factors that affect the distribution of organisms
• Measuring effect of abiotic factors on distribution


  1. Use a belt transect

  2. Place quadrats along the transect line

  3. Measure abundance of organisms and abiotic factors in each quadrat
• Changes in abundance can show which abiotic factor has the greatest effect on the organisms
• Adaptations


  Characteristics that make an organism suited to particular conditions
• If abiotic factors change


  The distribution of organisms may also change
• Few organisms can survive a drought (lack of water) for long
• Most land plants cannot survive if their roots are under water for long
• If the climate changes resulting in more flooding or more drought


  Many species in different communities may die out
• Temperature


  Affects the distribution of organisms
• Organisms adapted to different temperatures


  • Polar bears adapted to cold regions
  • Cacti adapted to hot deserts
• All organisms have adaptations that make them suited to life at particular temperatures
• A long-term rise or fall in temperature in an ecosystem


  Will change the distribution of some organisms and so affect the whole community
• Light is essential for plants and algae to grow
• In the oceans, most algae can only get enough light within 30 m of the surface
• In dense forests, few plants can grow on the forest floor
• Pollutants


  Substances that cause harm in the environment and cause pollution
• Many human activities release pollutants
• Pollution from the collapsed dam in Brazil killed fish and other river organisms
• Drought in an ecosystem


  Can have long-term effects on the animals in a community
• Clownfish


  Benefit from the relationship with a sea anemone
• Sea anemone


  Benefit from the relationship with a clownfish
• A sea anemone's stinging tentacles protect clownfish from predators. Clownfish chase off the predators of the anemone and provide nutrients in their faeces, which help the anemone to grow.
• Coral polyps


  Form a special relationship with single-celled algae
• The algae can live in the water surrounding corals, but are better protected inside a polyp. The algae photosynthesise and share the food they make with the coral animal.
• Some species of Wolbachia bacteria are parasitic. One species kills mosquitoes within a day of them feeding on blood containing the bacteria. Other Wolbachia species are mutualistic, increasing the ability of the host to reproduce.
• Some hosts (such as the roundworms that cause elephantiasis) cannot reproduce and will soon die unless they are infected with Wolbachia.
• Mutualistic relationship between coral animal and algae


  1. Algae live inside the coral

  2. Algae photosynthesise

  3. Algae share food with coral
• Parasitic


  Parasite is dependent on its host
• Mutualistic


  Both organisms benefit from the relationship
• Fish farming aims to produce more fish and so reduce overfishing of wild fish
• Fish farming


  A method of fishing. It works by growing fish in a contained area, usually to supply humans with food. It aims to produce more fish and so reduce overfishing of wild fish
• Fish farming causes problems because so many fish are kept in a relatively small space. Uneaten food, and faeces from the fish, sinks to the bottom of the water. This can change conditions, which may harm the wild organisms that live there. Parasites and disease spread more easily between fish in pens, so the fish need to be treated to keep them healthy.
• Introducing new species to ecosystems can affect the indigenous, or native, species (organisms that have always been there).
• Introduced species


  • Sheep
  • Cattle
  • Soybeans
• In the 2000s, sea lice from farmed salmon killed over 90 per cent of young wild salmon on one Canadian coast. Timing of treatment to kill the lice on farmed salmon was changed to just before the wild salmon passed through the area, reducing deaths of wild salmon to 4 per cent.
• Some species are introduced in order to affect an ecosystem, such as to reduce the numbers of another species that has got out of control. This often happens after humans have changed ecosystems and affected the food web.
• Eutrophication


  Addition of more nutrients to an ecosystem than it normally has